<form name="_xclick" action="https://www.sandbox.paypal.com/cgi-bin/webscr" method="post" id="myform">
<input type="hidden" name="cmd" value="_xclick">
<input type="hidden" name="business" value="xxxxxx_1310713211_biz@163.com">
<input type="hidden" name="item_name" value="For Search">
<input type="hidden" name="currency_code" value="GBP">
<input type="hidden" name="custom" value="<?php echo $this->key?>">
<input type="hidden" name="amount" value="<?php echo $this->paypalFee?>">
<input type="hidden" name="notify_url" value="<?php echo $this->fullBasePath.'/bbling/index/paypal-notify'?>" />
<input type="hidden" name="return" value="<?php echo $this->fullBasePath.'/' ?>">
<script>
document.getElementById('myform').submit();
</script> 
</form>